The present invention relates to a microspeaker used in a portable communication equipment such as a portable telephone and other equipments.
Referring to FIGS. 4 and 5 showing a conventional microspeaker, a yoke 2 made of magnetic material is embedded in a case 1 made of plastic by insert molding. A permanent magnet 3 is secured to the yoke 2, and a top plate 4 made of magnetic material is adhered to the magnet 3 to form a magnetic circuit and to form a magnetic gap between the top plate 4 and the yoke 2.
A vibrating plate 6 is secured to the case 1 at the periphery thereof. A voice coil 5 secured to the underside of the vibrating plate 6 is inserted in the magnetic gap. A protector 7 made of metal is secured to the case 1, interposing the vibrating plate 6. A plurality of sound discharge holes are formed in the case 1 and the protector 7.
A pair of ends 9 of the voice coil 5 are adhered to the underside of the vibrating plate 6 as shown in FIG. 4. Each of the ends 9 is outwardly extended from the case 1 passing through a groove formed in a peripheral wall of the case. On the underside of the case 1, a substrate 8 made of plastic is adhered, and a pair of terminal plates 10 are secured to the substrate 8. Each of the terminal plate has a V-shape and each end 9 is connected to one of the branches of the terminal plate 10 by solder 11. The other branch of the terminal plate 10 is used for connecting the end 9 to a circuit of the equipment to be mounted therein.
Thus, when a signal current is applied to the voice coil 5 through the terminal plates 10, the vibrating plate 6 vibrates to produce sounds.
In the conventional speaker, the voice coil 5 must be secured to the vibrating plate 6 before the vibrating plate is fixed to the case 1. However, since the vibrating plate 6 is made of a thin plastic film which is poor in stiffness, it is difficult to manipulate the vibrating plate, and to automatize the voice coil securing manufacturing process.
Furthermore, since the ends 9 of the voice coil are inserted between the case 1 and the protector 7, the vibrating plate 6 is slightly floated, which renders the adhesion of the vibrating plate irregular. In addition, the end 9 is stressed by the pressure for the adhesion of the vibrating plate.
An object of the present invention is to provide a microspeaker which may obviate the above described troubles.
According to the present invention, there is provided a microspeaker comprising a case comprised of an upper case and a lower case, a yoke made of magnetic material, a permanent magnet provided in the lower case, a vibrating plate secured to the upper case, a voice coil secured to an underside of the vibrating plate, and a protector plate secured to the upper case.
Each end portion of the voice coil is engaged in a groove formed in the upper case.
End portions of the voice coil are adhered to the underside of the vibrating plate.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.